QwtSplinePolynomial Class Reference

A cubic polynomial without constant term. More...

#include <qwt_spline_polynomial.h>

Public Member Functions
	QwtSplinePolynomial (double c3=0.0, double c2=0.0, double c1=0.0)
	Constructor.
bool	operator== (const QwtSplinePolynomial &) const
	Compare two polynomials for equality.
bool	operator!= (const QwtSplinePolynomial &) const
	Compare two polynomials for inequality.
double	valueAt (double x) const
	Calculate the value of a polynomial for a given x.
double	slopeAt (double x) const
	Calculate the value of the first derivate of a polynomial for a given x.
double	curvatureAt (double x) const
	Calculate the value of the second derivate of a polynomial for a given x.

Static Public Member Functions
static QwtSplinePolynomial	fromSlopes (const QPointF &p1, double m1, const QPointF &p2, double m2)
	Find the coefficients for the polynomial including 2 points with specific values for the 1st derivates at these points.
static QwtSplinePolynomial	fromSlopes (double x, double y, double m1, double m2)
	Find the coefficients for the polynomial from the offset between 2 points and specific values for the 1st derivates at these points.
static QwtSplinePolynomial	fromCurvatures (const QPointF &p1, double cv1, const QPointF &p2, double cv2)
	Find the coefficients for the polynomial including 2 points with specific values for the 2nd derivates at these points.
static QwtSplinePolynomial	fromCurvatures (double dx, double dy, double cv1, double cv2)
	Find the coefficients for the polynomial from the offset between 2 points and specific values for the 2nd derivates at these points.

Public Attributes
double	c3
	coefficient of the cubic summand
double	c2
	coefficient of the quadratic summand
double	c1
	coefficient of the linear summand

Detailed Description

A cubic polynomial without constant term.

QwtSplinePolynomial is a 3rd degree polynomial of the form: y = c3 * x³ + c2 * x² + c1 * x;

QwtSplinePolynomial is usually used in combination with polygon interpolation, where it is not necessary to store a constant term ( c0 ), as the translation is known from the corresponding polygon points.

See also

QwtSplineC1

Constructor & Destructor Documentation

QwtSplinePolynomial()

QwtSplinePolynomial::QwtSplinePolynomial ( double  a3 = 0.0, double  a2 = 0.0, double  a1 = 0.0  )

inline

Constructor.

Parameters

[in]	a3	Coefficient of the cubic summand
[in]	a2	Coefficient of the quadratic summand
[in]	a1	Coefficient of the linear summand

Member Function Documentation

curvatureAt()

double QwtSplinePolynomial::curvatureAt ( double  x ) const

inline

Calculate the value of the second derivate of a polynomial for a given x.

Parameters

[in]

x

Parameter

Returns

Curvature at x

fromCurvatures() [1/2]

QwtSplinePolynomial QwtSplinePolynomial::fromCurvatures ( const QPointF &  p1, double  cv1, const QPointF &  p2, double  cv2  )

inlinestatic

Find the coefficients for the polynomial including 2 points with specific values for the 2nd derivates at these points.

Parameters

[in]	p1	First point
[in]	cv1	Value of the second derivate at p1
[in]	p2	Second point
[in]	cv2	Value of the second derivate at p2

Returns

Coefficients of the polynomials

Note

The missing constant term of the polynomial is p1.y()

fromCurvatures() [2/2]

QwtSplinePolynomial QwtSplinePolynomial::fromCurvatures ( double  dx, double  dy, double  cv1, double  cv2  )

inlinestatic

Find the coefficients for the polynomial from the offset between 2 points and specific values for the 2nd derivates at these points.

Parameters

[in]	dx	X-offset
[in]	dy	Y-offset
[in]	cv1	Value of the second derivate at p1
[in]	cv2	Value of the second derivate at p2

Returns

Coefficients of the polynomials

fromSlopes() [1/2]

QwtSplinePolynomial QwtSplinePolynomial::fromSlopes ( const QPointF &  p1, double  m1, const QPointF &  p2, double  m2  )

inlinestatic

Find the coefficients for the polynomial including 2 points with specific values for the 1st derivates at these points.

Parameters

[in]	p1	First point
[in]	m1	Value of the first derivate at p1
[in]	p2	Second point
[in]	m2	Value of the first derivate at p2

Returns

Coefficients of the polynomials

Note

The missing constant term of the polynomial is p1.y()

fromSlopes() [2/2]

QwtSplinePolynomial QwtSplinePolynomial::fromSlopes ( double  dx, double  dy, double  m1, double  m2  )

inlinestatic

Find the coefficients for the polynomial from the offset between 2 points and specific values for the 1st derivates at these points.

Parameters

[in]	dx	X-offset
[in]	dy	Y-offset
[in]	m1	Value of the first derivate at p1
[in]	m2	Value of the first derivate at p2

Returns

Coefficients of the polynomials

operator!=()

bool QwtSplinePolynomial::operator!= ( const QwtSplinePolynomial &  other ) const

inline

Compare two polynomials for inequality.

Parameters

[in]

other

Other polynomial

Returns

true, when the polynomials have different coefficients

operator==()

bool QwtSplinePolynomial::operator== ( const QwtSplinePolynomial &  other ) const

inline

Compare two polynomials for equality.

Parameters

[in]

other

Other polynomial

Returns

true, when both polynomials have the same coefficients

slopeAt()

double QwtSplinePolynomial::slopeAt ( double  x ) const

inline

Calculate the value of the first derivate of a polynomial for a given x.

Parameters

[in]

x

Parameter

Returns

Slope at x

valueAt()

double QwtSplinePolynomial::valueAt ( double  x ) const

inline

Calculate the value of a polynomial for a given x.

Parameters

[in]

x

Parameter

Returns

Value at x

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The documentation for this class was generated from the following file:

• /home/runner/work/QWT/QWT/src/plot/qwt_spline_polynomial.h